Millstone.



- PATENTED JUNE 16, 1908.

a No. 891,050.

J. L. DURHAM.

MILLSTONE.

No. 891,050. I PATENTED JUNE 16, 1908. J. L. DURHAM.

MILLSTONE.

l y 2 x 4 w ML nn M ' 44 in Fig. 1.

JOHN L. DURHAM, OF SANCO, TEXAS.

MILLSTONE.

Application filed December 4, 1905.

Specification of Letters Patent.

Patented June 16, 1908.

Serial No. 290,261.

To all whom it may concern.

Be it known that I, JOHN L. DURHAM, a citizen of the United States,residing at Sanco, in the county of Coke and State of Texas, haveinvented new and useful Imrovements in Millstones, of which the folowingis a specification.

This invention relates to millstones and it has for its object toprovide an improved millstone dress which shall be conducive to the bestresults in assuring a thorough grinding of the grain; in securing auniform grade of product; and in increasing the capacity of the stonesfor work.

With these and other ends in view which shall readily appear as thenature of the invention is better understood, the same consists in theimproved millstone dress which will be hereinafter fully described andparticularly pointed out in the claims.

In the accompanying drawings, Figure 1 is a plan view .of a ortion ofthe upper stone dressed in accor ance with the invention; only thatportion of the stone being. shown which is closely adjacent to the eye,the stone being shown in inverted position so as to ex ose the workingface. Fig. 2 is a sectionafview taken on the plane indicated by the line22 in Fig. 1, and the stone being shown in inverted position. Fig. 3 isa sectional view taken on the plane indicated by the line 33 in Fig. 1.Fi 4 is a sectional view taken on the plane indicated by the line Fig. 5is a .plan of a bed stone dressed in accordance with the invention. Fig.6 is a vertical sectional view showin the bed stone and the upper stoneassemb ed in running position.

Corresponding parts in the several figures are denoted by likecharacters of reference.

The two millstones which are designated as the upper stone 1 and the bedstone 1 are dressed precisely alike, and the descri tion of one willapply to both. Each 0 the stones is provided with an annular groove orchannel 4 which, in the upper stone is formed immediately adjacent tothe eye 2; the said groove or channel being formed in a correspondinglocation in the lower stone, as will be clearly seen by reference toFig. 6.

In accordance with the invention there is formed in the working face ofeach stone a plurality of feed ducts 5, preferably tangential to theannular groove or channel 4, and comprising grooves or channels that areapproximately V-shaped in cross-section, as

working face of the stone.

best seen in Fig. 3. These grooves, which constitute the feed grooves,are of an extreme length approximately equal to, but not exceeding thediameter of the eye, and said grooves are at their inner ends of anextreme depth which is less than that of the annular groove or channel4, while at their outer extremities they merge with the face of thestone the bottoms 6 of said grooves being inclined and dying orshallowing into the general plane of the grinding surface, as will beclearly seen in Fig. 4. The edges or walls, 7, of the grooves or ducts 5are formed at approximately right angles to the working face of thestone while, owing to the cross-sectional V-shape of said ducts theirrear edges merge with the face of the stone; said rear edges beingpreferably rearwardly concaved as will be seen at 8, so that the bottomsof the ducts will merge very gradually into the These ducts inconnection with the annular channels 4 constitute the entire millstonedress; and the usual feed ducts which extend nearly or quite to theperipheral edges of millstones as ordinarily dressed, are entirelyomitted.

When the stones, dressed in accordance with the invention, areassembled, as shown in Fig. 6, grain fed through the eye of the stonewill pass into the space formed by the annular channels 4, said spaceconstituting a receptacle from which the grain, by the centrifugalaction set up by the rotation of one of the stones, is dischargedbetween the working faces of the stones, being subjected to a gradualreduction process between the bottoms 6 of said feed ducts which, asstated, merge with the working faces of the stones. The ducts 5 being ofan extreme length which is only approximately equal to but not exceedingthe diameter of the eye, and the latter, which is selected as a unit ofmeasure for the purpose of establishing the proortionate dimensions ofthe ducts with reation to the stones being usually of a diameter notexceeding one-twelfth of the total diameter of the stone, it followsthat a relatively very small or minimum proportion of the entire workingfaces each of which lies in one general plane, of the stones is furrowedby these ducts, or leading furrows, and that the grain, afterpreliminary reduction by the shearing action between the inclinedbottoms of the ducts on the opposing faces, will be immediatelysubjected to the action of the extended working faces, which occupy arelatively very large proportion of the total faces of the stones. Ihave found by practical demonstration that, by this construction of themillstone dress, a much more uniform product is secured than wherelarger proportions of the faces of the stones are grooved or furrowed;the material may be ground without objectionable heating of the product;and the speed of the operation is largely increased.

Having thus fully described the invention, what I claim as new is 1. Amillstone having a grinding face comprising a general surface lying. ina single plane, and a dress consisting essentially of an annulardepression or feed groove in its central region having exits in the formof leading or feeding furrows extending tangentially from said groove ina direction inclining backward from the direction of rota' tion, and ofa length not greater than the diameter of the annular groove; saidfurrows having inclined bottoms shallowing outwardly and rearwardly intothe general plane or face of the stone, substantially as specified.

2. The combination of a pair of millstones each having a grindingsurface lying in one general plane, a central annular depression orfeeding groove, and feeding furrows leading therefrom and tangentialthereto, having a length no greater than the diameter of said annulargroove and dying rearwardly into the general plane of the surfacewhereby the grain as it is fed outwardly receives a shearing orpreliminary grinding action from the two sets of grooves, and a maximumproportion is. secured of coacting grinding surfaces each lying in onegeneral plane, substantially as specified.

In testimony whereof, I aflix my signature in presence of two witnesses.

JOHN L. DURHAM.

